The present invention relates to a mobile communication system arranged to provide IP packet communications, and more particularly to a method for routing IP packets which allows any data terminal for doing IP packet communications between IP networks to keep itself in communication without changing an IP address allocated to it.
A mobile communication system, represented as a cellular phone system, has been mainly used as phones. In parallel, the mobile communication system is being increasingly implemented as the use of a short message with data communications. With recent prevail of a data terminal such as a note-sized personal computer to be easily carried and increase of functions of a mobile station such as a mobile phone, a request has been rising for connecting a mobile station to an IP network such as a LAN in an enterprise or an internet.
Under this condition, a packet communication (DoPa) system of 28.8 Kbps has started in a personal digital cellular (PDC) on March 1997 in Japan. This system is standardized as PDC mobile packet communication system (PDC-P) by the ARIB (Association of Radio Industries and Businesses) and as described in xe2x80x9cOverview of PDC-P Systemxe2x80x9d, NTT DoCoMo Technical Journal, vol. 5, No. 2, July 1997, pp. 6-9.
The system is mainly used for connecting with an in-house LAN and an internet provider. The data terminal has an IP address for supporting a fixed address and a dynamic address. The supported fixed address enables the PDC to use an in-house private address.
The PDC system may accommodate lots of in-house LANs and providers. However, it limits a connecting destination of each mobile station (end user) to a pre-registered network. That is, the connecting point of the mobile station in the in-house LAN or the internet provider is fixed. The data terminal may directly use the application running on the IP, so that in the PDC it uses a protocol called the PPP (Point-to-Point Protocol) on the transfer protocol inside of the PDC network for realizing transfer of the IP packets.
On the other hand, the mobile IP regulated in the standards advisory document Network Working Group RFC (Request for Comments): 2002, by C. Perkins, IETF (Internet Engineering Task Force), Aug. 29, 1997, pp. 1-59 has been proposed for the purpose of realizing the movement transparent IP communication. The mobile communication system such as a cellular system uses an identifier of a mobile station or a user for managing movement of the mobile station. On the other hand, the mobile IP has a home agent function and a foreign agent for each subnetwork. The mobile IP manages the movement of an IP address of a data terminal connected to the mobile station, for realizing transfer of IP packets in an end-to-end manner.
The mobile IP manages the movement with the IP address of the fixed data terminal as a base, while the system for wirelessly transferring packets as disclosed in JP-A-9-326805 is executed to assign the corresponding IP address to a destination wireless system to each data terminal without assigning the fixed IP address to each data terminal. This disclosure has further proposed a system for managing the assigned IP address in correspondence to the mobile station connected with the data terminal or a user identifier in a home network to which the data terminal belongs and obtaining an IP address of a destination from the home network when transferring data.
The mobile communication system may implement a transfer rate of 384 Kbps as a minimum rate in a wide range environment by means of a new wide-band access technique at a radio frequency of 2 GHz. In the indoor environment, the system may implement a transfer rate of 2 Mbps as a maximum rate. This indicates the implementation of fast data communications in this mobile communication system. Accordingly, it is presumed that the user""s request for the mobile communication system is gradually changed from fast internet access to transfer of multimedia data, transfer of real-time video data, and then a virtual private network. The data communication is hence indispensable to the mobile communication system.
In the near future, the technical and social position of the data communication is changed from an additional service to a phone system to the corresponding service to the phone system itself, so that more persons are likely to use the data communication. In particular, the connection with the internet is an essential function to the packet data communication service.
In the PDC-P system, each mobile station (end user) has the corresponding fixed route to the in-house LAN or the internet. Hence, the PDC-P system has a first problem that it limits the access to the IP network and has difficulty in entering the global roaming.
As a second problem, if a mobile IP is applied to the existing mobile communication system, the PDC-P system is required to perform the double methods, that is, the existing method for managing movement of a mobile station and a new method for managing movement of a data terminal with an IP address. This means an increase of an overhead in managing movement of a mobile station.
Today, the internet is mainly used for send and receive of mails and access to the World Wide Web. In coming several years, the internet will be newly used for information distribution by the push technique or download of an application from an object store server. In particular, about the information distribution, attention should be paid to the change of the data transfer process from the current data terminal initiative to the coming network initiative.
Considering these ways of use, the system for assigning to each data terminal the corresponding IP address to the destination, as proposed in JP-A-9-326805, has the following problems. If the data transfer is started from the network, the access to the home network is required for obtaining the IP address of the data terminal. Hence, the system disclosed in JP-A-9-326805 is required to solve the problem for reducing an overhead burdened in retrieving the IP address as well as obtaining the latest IP address of the terminal from a fixed IP network such as the internet.
It is therefore an object of the present invention to provide implementation of IP packet transfer through an efficient route in a mobile communication system.
It is a further object of the present invention to provide implementations of IP packet transfer based on the existing management of movement in a mobile communication system and start of the packet transfer enabled by a network.
According to a feature of the present invention, plural contacts are provided between the mobile communication system and the IP network. The connection of the mobile communication system at each of the contacts is executed by a packet gate way having a router function so that an area of the mobile communication system is arranged of plural IP subnetworks in correspondence to the packet gate ways located inside of the mobile communication system.
According to another feature of the present invention, a request for registering a location of a mobile station includes an IP address of a data terminal connected to the mobile station. A visitor location register manages both the location information of the mobile station and the IP address of the data terminal connected with the mobile station. Together with it, an area of the mobile communication system is divided into plural IP subnetworks so that the location information of the mobile station and the IP address of the data terminal connected to the mobile station are notified to the corresponding packet way to the IP subnetwork where the mobile station is located (IP subnetwork containing a radio cell where the mobile station is located).
According to another feature of the present invention, the packet gate way manages the IP address and the location information notified from the visitor location register. If the notified IP address does not belong to the corresponding IP subnetwork to the packet gate way, the packet gate way (home packet gate way) corresponding to the IP subnetwork where the notified IP address belongs is identified. The notified IP address and the IP address of the packet gate way (that corresponds to the destination packet gate way as viewed from the home packet gate way) are notified to the identified home packet gate way.
According to another feature of the present invention, when receiving the IP packet, the packet gate way compares the IP address of the sending destination with the IP address managed by the packet gate way itself in correspondence to the location information. If the packet gate way itself manages the IP address that matches to the received IP address, the IP packet is transferred on the corresponding location information to the IP address. As a result of the comparison, if the received IP packet is determined to be the IP packet destined for the data terminal connected to the mobile station moved to the corresponding IP subnetwork to another packet gate way, the IP packet is transferred to the destination packet gate way.
According to another feature of the invention, plural packet gate ways are connected between the mobile communication system and the IP network. Hence, the corresponding IP subnetworks to the packet gate ways may be built in the mobile communication system.
In this type of mobile communication system, the send and receive of IP packets to and from the data terminal connected to the mobile station is executed by the corresponding packet gate way to the IP subnetwork where the mobile station is located. Considering the increase of the users of the data communication in the near future, the transfer of IP packets may be implemented through an efficient route.
According to another feature of the invention, the request for registering a location of the mobile station contains the IP address of the data terminal connected to the mobile station. This results in implementing the transfer of IP packets based on the existing management of the movement of the mobile communication system. Further, since the IP address may be fixed to each data terminal, the packet transfer may be started by the network initiative.